The invention relates to a set for extracorporeal circulation of blood and to a procedure for filling and rinsing the set with a physiological solution.
Specifically, though not exclusively the invention can be usefully applied in performing a priming of an extracorporeal circuit used in an apparatus for extracorporeal blood treatment, such as for example a dialysis machine, a hemoperfusion device, a blood oxygenator, a blood component separator, and the like.
As is well known, before performing a dialysis operation, the extracorporeal blood circuit of the dialysis equipment must be filled with an isotonic fluid, normally a sodium chloride solution with a concentration of 155 mmol/l. This procedure, normally known as priming, has the objective of rinsing the circuit and removing the air and any particles and sterilizing fluid left in the circuit.
The prior art includes a priming set predisposed to supply the isotonic solution to the extracorporeal blood circuit both during the priming stage, before treatment, and during the treatment itself, and also following treatment. During treatment (for example during a dialysis session) the isotonic solution can be injected into the extracorporeal blood, for example in a case of patient hypertension or as a dilutor during administration of a medicinal substance. The isotonic solution can also be used in treatment for the movement of the extracorporeal blood being returned to the patient.
The prior art includes an extracorporeal circuit (for example a dialysis set) which is made in two parts, an arterial part and a venous part, each of which has a first end provided with a connector to the patient for connection to a vascular access, and a second end having a device connector for connection to a blood treatment device (dialyser). During treatment the arterial part receives the blood from the patient and sends it to the blood treatment device, while the venous part receives the treated blood from the device and returns it to the patient. Normally the arterial part includes a branch tube for administration of the saline, which tube typically terminates in a female luer connector for connection to an end of the priming set. During the priming procedure the extracorporeal circuit is connected to the blood treatment device and the priming set is connected to the branch tube. In a first priming stage the saline fills the arterial zone comprised between the patient connector and the branch tube. During this stage the patient connector is open to enable expulsion of air from the circuit. In a second stage the rest of the circuit is filled up to the patient end of the venous part. Between the first and the second stages the patient connector of the arterial line must be closed and manual clamps are activated to direct the saline in the right direction. This known priming process is however very long and laborious as it requires two successive stages which are further separated by a stage of clamping and unclamping. Also, as the interruption of the first stage must be done in a timely fashion in order to avoid excessive exiting of liquid from the patient connector, the operator must be especially focused on the task in hand.
In another known priming procedure the patient end of the arterial line is connected directly to a bag of saline, after which the saline can fill the whole extracorporeal circuit up to the patient connection of the venous line in a single stage. Thereafter the priming set is detached from the patient end of the arterial line and connected to the branch tube of the arterial line until the saline is ready to be used during treatment. As at the end of each priming procedure, and before starting treatment the arterial line has to be connected to the vascular access of the patient, in the case described herein the patient connection to the arterial line is exposed to risk of contamination as soon as the priming set is detached (and is therefore still wet) and before being connected to the patient.
U.S. Pat. No. 6,387,069 describes an extracorporeal blood transport set comprising a first branch line which branches off from a first branch point in an intermediate zone of the arterial line and which in a priming stage is connected to a source (a bag) of saline. The first branch line exhibits a second branch point to which a service connector is connected, directly or via a second branch line, which service connector is predisposed to be connected with the patient connector of the arterial line. U.S. Pat. No. 6,387,069 also describes a procedure for priming the above-cited extracorporeal blood transport set, according to which the patient connector of the arterial line is connected to the service connector in order to form a closed loop comprising: the service connector with, if present, the second branch line; the part of arterial line comprised between the patient connector and the first branch point; and the part of first branch line comprised between the first and second branch points. In this priming configuration the saline can perform the filling and rinsing of the part of arterial line comprised between the patient connection and the first branch point. This priming procedure also exhibits various drawbacks. Firstly the preliminary operation of connecting the patient connector to the service connector involves a risk of contamination of the arterial line which will then be connected to the patient. Secondly the transport set must be provided with a relatively complicated valve system, both in structural and practical terms, during the priming, because of the selective closure of the first branch line (between the first and second branch points) and the service connection (or the second branch line if present). Also, the presence of a service connection as well as the first branch line in itself represents a complication.
U.S. Pat. No. 6,770,049 discloses a blood set for extracorporeal blood circulation comprising an arterial line, a venous line, a priming inlet line which branches off from the arterial line, and a priming liquid return line which branches off from the venous line. U.S. Pat. No. 6,770,049 further describes a filling procedure of the blood set in which the inlet line of the priming liquid is connected at one end to a container of the priming liquid and at the other end to the priming liquid return line. The arterial patient end and the venous patient end are closed by respective security caps provided with a hydrophobic membrane which is permeable to gas but not to liquids. During the priming procedure, the air contained in the blood set is released through the hydrophobic membrane in order to enable complete filling of the blood set without the liquid's escaping. However, the use of special security caps has a negative effect on the cost of the blood set. Furthermore the priming procedure is complicated by the need for a stage of removing and discarding the security caps before setting up the blood set connection to the patient.